The Internet has become a major source of information. At any given time, hundreds of thousands of clients are downloading information from various servers on the Internet. For any given server, an important technical issue is the number of clients it is able to serve at a given time. Unacceptable delay may be experienced if the number of client requests significantly exceeds the capacity of the server.
This issue of server capacity is critical in the case of streaming media content. Recently, there has been an explosive growth of streaming media applications on the Internet. With a typical streaming media application, video and/or audio data are streamed from a server to a requesting client for playback by the client. Since the video and audio data are continuously transmitted at a relatively high rate, streaming media content places a significant demand on the server's bandwidth. An especially difficult technical challenge is the server's ability to handle transient surges in the number of clients requesting the streaming media data. A sudden surge of the number of requesting clients, also called a “flash crowd,” is often experienced after the occurrence of a significant event of widespread interest, such as a major earthquake or terrorist attack. Due to the high bandwidth demand of streaming media content, the large number of requests in a flash crowd situation can easily overwhelm a server.
There has been much work in recent years on the topic of efficient content distribution. That work has largely fallen into two categories: infrastructure-based content distribution and peer-to-peer content distribution. An infrastructure-based content distribution network (CDN) (e.g., the Akamai network) complements a server in a traditional client-server framework by employing a dedicated set of machines to store and distribute content to clients on behalf of the server. Even though a large well-engineered CDN could handle a large flash crowd effectively, such a solution is unlikely to be affordable for a large class of sites that only rarely experience a significant volume of load. A peer-to-peer content network (e.g., Napster and Gnutella), in contrast, relies on clients to host the content and distribute it to other clients and typically has no central server that holds the content. Thus, it does not address the issue of how to enable a server to distribute streaming media content to a large number of clients during a transient surge of requests.